Cooking oil employed for the cooking of various foods must be periodically filtered in order to remove accumulated particulate matter and thereby permit repeated use of the cooking oil. Generally, it is desirable to perform such filtering operations directly in a kitchen of a cooking establishment so that after the cooking oil is filtered, it may be returned to the cooking vessel for immediate reuse. In many instances, it is also desirable to perform the filtering operation while the oil is hot, i.e., at an elevated temperature immediately after it has been used for cooking, so as to minimize the down-time of the cooking vessel. However, because the oil is hot, there is a risk of hazards and possible injury to personnel during the filtering operation. Consequently, various filtering methods and systems have been suggested which seek to minimize the chances of hot oil coming in contact with the operator or user during the filtering operation.
Some of the known filtration systems require significant suction or pressure requirements for drawing the hot cooking oil from the cooking vessel and forcing it across a suitable filtering medium. These systems consequently require relatively large pumping mechanisms and closed fluid systems for developing and maintaining the required pressure levels, and therefore are relatively expensive and complicated in nature.
Other filtering systems and methods are known which employ filter bags or members which operate on the principal of gravity, i.e., in which the hot cooking oil is simply discharged into the bag or member and allowed to pass therethrough by gravity, the particulate matter being collected in the bag and the filtered oil being discharged into a safety drain pot. However, even with these gravity type filtering systems, relatively large and bulky pumping apparatus have been required as well as specialized equipment and operations for removal of the cooking oil from the cooking fryer and subsequent return of the filtered cooking oil to the fryer.
For example, gravity type filtering systems have been employed with cooking vessels or fryers which are equipped with a drain valve for draining cooking oil from the fryer into an appropriate filter bag or member which serves to remove crumbs, sediment and other particulate matter from the oil before passing it into a collection vessel or drain pot. A rotary-pump apparatus having a suction hose and discharge hose is then employed to suck filtered oil from the drain pot through the suction hose and to then pump it through the discharge hose back into the fryer. Generally, a further filtering member is employed to receive the filtered oil from the discharge hose to provide a secondary filtering operation before the oil is returned to the cooking fryer.
A different but similar filtering system has also been employed with respect to cooking fryers which are not equipped with a drain valve. With these types of cooking fryers, the filtering system includes a rotary pump having a suction/discharge hose equipped with a nozzle for direct insertion into the cooking fryer for initially sucking hot oil from the cooking fryer through the suction/discharge hose and discharging it through a discharge tube into a first-stage filtering member which serves to filter out crumbs, sediment and other particulate matter and to discharge the filtered oil into a drain pot. When it is desired to return filtered oil to the cooking fryer, the discharge tube is replaced with a second suction hose, and the pump is reversed to then suck oil from the drain pot and discharge it through the suction/discharge hose into the cooking fryer. Again, a secondary filter member can be employed for receiving oil being pumped from the drain pot before its discharge into the cooking fryer.
With both of these latter types of prior art filtration systems, rotary-pumping apparatus which are relatively large and bulky are employed for pumping oil from one vessel into another vessel. Because rotary-pumping apparatus have the capability of greatly increasing the energy imparted to the fluid being pumped, if the suction and/or discharge hoses should become clogged, there is a possibility of a significant pressure build-up being developed in the oil which, in some instances, can cause the hoses to burst or leak, thereby spewing hot oil out of the hose and possibly injuring personnel in the kitchen. Thus, relatively thick-walled tubing must generally be employed in order to minimize these hazards. Also, such rotary-pumping apparatus, while performing adequately in most instances, do tend to produce significant wear on the pump parts, thereby requiring replacement or reservicing of the pump. Additionally, because such pumps require shaft seals, they are generally relatively expensive. Still further, with cooking fryers which are not equipped with drain valves, the filtering operation requires that the rotary pump be capable of operating in reverse, and additionally requires the changing of tubes and hoses in order to effect filtering of the oil and then the subsequent return of filtered oil to the fryer.
Accordingly, it is an object of the present invention to provide an improved method and system for filtering cooking oil in cooking fryers which is more reliable and of a simpler design and operation, and which achieves the same or superior degree of effectiveness and performance as prior art filtering systems and methods.